This invention relates to microwave interactive materials. It also relates to microwave interactive coatings.
The cooking of food and heating of substances with microwave radiation has become increasingly popular and important in recent years because of its speed, economy, and low power consumption. With food products, however, microwave heating has drawbacks. One of the major drawbacks is the inability to brown or sear the food product to make it similar in taste and appearance to conventionally cooked food.
Several methods have been attempted in the prior art to overcome the browning problem. One such method for browning food and other materials involves the use of a metalized coating on paperboard. The prior art process for manufacturing this coated paperboard required several steps.
First, metal particles are vacuum deposited onto a film, preferably a polyester film. The film is then laminated onto the paper. The thus metalized paper, typically, must then be positioned onto a particular part of the food package, requiring a relatively complicated windowing operation.
The windowing operation requires that the metallized paper be slit before entering the process. The windowing process also can only create rectangular shaped laminates.
Besides the complexity of the prior art process, there are several other disadvantages. With vacuum deposition, it is difficult, if not impractical, to develop a specific pattern or shape to the coating applied which would be useful for controlling the heating of the food product. It is also difficult in the deposition process to vary the coating formulation or coating thickness in localized areas of the film to meet different heating requirements. This is particularly important when heating different foods together in a microwave oven.